1. Field of the Invention
The present invention relates to a power saving technique for an electrophotographic image forming apparatus, and more particularly a gradational power saving technique for reducing power consumption step by step with the passage of a print-waiting time.
2. Description of the Related Art
An electrophotographic image forming apparatus, such as a laser printer and copying machine, maintains a constant fixing temperature near to a printing temperature during a print-waiting state, in order to quickly restart a printing operation. The laser printer or the coping machine utilizes a heat lamp for providing a high temperature during a process of fixing a toner on a paper. As stated above, since the heat lamp is continuously turned on, power consumption is undesirably increased. However, in the electrophotographic image forming apparatus, the print-waiting time is normally much longer than an actual printing time. Nevertheless, the heat lamp is continuously heated even during the print-waiting state, causing an unnecessary power consumption. Therefore, in order to solve such s problem, various techniques have been proposed. For example, an earlier electrophotographic image forming apparatus employs a power saving mode in which the heat lamp and a fan motor are completely turned off if a predetermined time has passed during the print-waiting state, in order to reduce the unnecessary power consumption.
A laser printer, which is a typical electrophotographic image forming apparatus, includes a video controller and an engine. The video controller includes a personal computer interface, a controller, an engine interface, an operating panel, a random access memory, and a read only memory. The personal computer interface interfaces an input/output signal with a personal computer. The controller performs data communication with the personal computer through the personal computer interface and controls the engine according to various control commands received from the personal computer and the operating panel so as to control the overall operation of the system. The engine interface interfaces an input/output signal with the engine under the control of the controller. The operating panel includes a plurality of keys for generating key data, provides the controller with the key data and displays display data generated by the controller. Under the control of the controller, the random access memory temporarily stores image data received from the personal computer interface and various data generated while the controller controls the printing operation. The read only memory stores software control programs for the controller. The engine, comprised of a driving mechanism for transferring the paper and printing the image data, controls the driving mechanism and an engine member according to the control of the control to perform the printing operation.
In the system noted above, the controller increases the fixing temperature of the engine up to a print waiting temperature and maintains the print waiting state. The controller checks whether or not the printing data or control command data has been received from the personal computer interface and the operating panel. If the printing data or the control command data has not been received, the controller counts the print waiting time to increase a counting value. This counting value is compared with a reference value for entering the power saving mode. If the counting value is less than the reference value, the process flow returns to the previous checking step of the controller and otherwise, if the counting value is equal to or greater than the reference value, the controller performs the power saving mode and then returns to the checking step. Meanwhile, if the printing data or the control command data has been generated, the controller resets the counting value and then a determination is made as to whether or not the current operation mode is the power saving mode. If it is not the power saving mode, a corresponding processing routine is performed. Namely, the controller performs an operation corresponding to the key input or pints the printing data. Otherwise, if it is the power saving mode, the controller repeats the previous step to increase fixing temperature of the engine up to the printing temperature and thereafter, the controller executes the processing routine step.
Unfortunately, in the above-noted system, the heat lamp is completely turned off in the power saving mode. While this saves power, it takes a considerable length of time, e.g., fifty seconds, for the printing temperature to reach its proper value when the system is switched from the power saving mode to the printing mode. This long delay creates considerable problems for the user.
The following patents each disclose features in common with the present invention but do not teach or suggest the incremental control of the print waiting temperature in accordance with the present invention.
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